The present invention relates generally, as indicated, to a comparison type colorimeter and, more particularly, to such a colorimeter that has improved accuracy in the optics portions thereof. Moreover, the present invention is directed to an enclosed stabilized light source to generate a uniform light output for use in such a comparison type colorimeter.
One source of error in photosensitive measuring instruments is encountered when light is directed onto different surface area portions of the photosensor, such as a photosensitive transistor, since equal intensities of light directed onto different surface area portions of a photosensor usually will produce different electrical outputs. Another source of error particularly in comparison type colorimeters has been encountered due to changes in the spectral properties of the color filters due to aging with the effects of such aging often being different for different respective filters and even for different respective portions of the same filter. Also, it has been found that the accumulation of dust on the lamp, reflector, and other elements of the light source of conventional colorimeters may cause a change or shift in the illumination output therefrom, thus causing still further error in the accuracy of the colorimeter.